1. Field of the Invention
The present invention relates to a transducer, and more particularly, to a transducer including a permanent magnet that generates a magnetostatic field, a patch disposed below the permanent magnet and formed of a material that deforms according to a variation in a magnetic field, an insulator disposed on a top surface of the patch, and a coil wound on the patch and the insulator in a certain form and inducing a magnetomotive field on the patch according to an applied current, in which the form of winding the coil is configured to be a form by which directions of the magnetostatic field generated by the permanent magnet and the magnetomotive field generated by winding the coil are orthogonal to each other.
2. Description of the Related Art
Magnetostriction, also referred to as the Joule effect, is a phenomenon in which a mechanical strain occurs when a ferromagnetic material is located under a magnetic field. As an inverse phenomenon thereof, a phenomenon, in which a magnetic state of the inside of a material varies when a stress acts on the material, is referred to as an inverse magnetostrictive effect or a Villari effect.
Since transducers using a magnetostriction effect may measure a deformation of an object with on mechanical contact with the object, the transducers have been used in several fields in which it is impossible to apply contact-type sensors. When using the magnetostriction effect, it is possible not only to generate elastic waves with no contact but also to generate elastic waves having larger magnitudes than those of methods using a typical piezoelectric effect.
Since omni-directional transducers may generate waves having the same magnitude and mode in all directions, when applying omni-directional transducers to phased array systems, it is possible to efficiently focus waves by using the same algorithm with respect to all directions. However, typical omni-directional transducers generally generate and measure Lamb waves, which have several limitations in comparison with shear-horizontal waves, fundamental mode (SH0 mode) of which has non-dispersive property. Accordingly, it is necessary to develop magnetostrictive patch transducers capable of efficiently generating and measuring shear-horizontal waves.